Stabilized mineral oil



an ica 4; U Patented June 6, 1939 UNITED STATES PATENT OFFICE STABILIZED MINERAL OIL Robert C. Moran, Wenonah, and Everett W.

Fuller, Woodbury, N. J., assignors to Socony- Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application August 1, 1936, Serial No. 93,762

8 Claims.

This invention is directed to the stabilization of hydrocarbon oils of higher boiling points against the deteriorating effects of oxidation reactions encountered under conditions of use. Moderately refined oils, such as moderately refined motor oils and other moderately refined lubricating oils and moderately refined turbine oils normally used under conditions of exposure to oxidation, oxidize, giving rise to sludge and/or acidic oxidation products frequently corrosive to the metals which they encounter in use, as for example bearing metals in automotive use, and copper and copper alloys in turbine use. Highly refined oils of the nature of transformer oils, cable and other insulating oils, and highly refined turbine oils are also found to deteriorate similarly, with loss of lubricating and/or dielectric properties due to the presence of sludge formed by oxidation. Such troubles becomes more pronounced with oils refined by more modern methods, as solvent refining, which is a process of producing an Oil of a more highly parafiinic nature by treating it with a solvent liquid exhibiting preferential solvent power for chemically difierent classes of constituents of the original oil, resulting in the production of oils of higher viscosity index. This power is possessed by numerous liquid reagents, for example, dichlorodiethylether, cresylic acid, phenol, chloraniline, chlorophenol, phenetidine, benzyl alcohol, nitrobenzene, benzonitrile, furfural, aniline, benzyl acetate, liquid sulphur dioxide, mixture of liquid sulphur dioxide or aniline with benzol, and the like. The oils so produced are definitely superior from almost all standpoints for automotive and other lubricating uses. It has been found, however, that such highly solvent refined motor oils are definitely corrosive under normal conditions of use, due to oxidation during use, to many bearing metals and other metals in contact with which they must be used. This also occurs in good paraffinic base oils which have not been subjected to solvent refining. The higher the VI, (viscosity index, a sign of paraillnicity), of the lubricating oil, the more pronounced is the corrosive tendency, as referred to above. Generally speaking, the problem is encountered in oils having a VI of or higher, becomes acute in oils having a VI of to 85, and very pronounced in oils of VI or higher. The tendency to formation of corrosive materials by oxidation of such oils is distinctly troublesome in the presence of the newer bearing metals, such as for example, cadmium-silver alloy bearings, or others such as copper-lead alloys, copper-lead-tin alloys, cadmium-nickel alloys, cadmium-zinc alloys, cadmium-zinc alloys modified by the presence of lead, antimony, or both, or a general class of alloys consisting principally of lead and hardened with calcium, barium, potassium, antimony, and the like, known generically as "high lead babbitts.

This invention has for its object the stabilization of such refined high boiling petroleum fractions against deteriorating effects of oxidation. It is also an object of this invention to alter or modify a highly refined oil, normally corrosive under conditions of use, by the use of an additive ingredient capable of substantially inhibiting this corrosion. It is a further object to provide a substantially non-corrosive motor oil of high VI. Another object is the provision of a refined dielectric oil resistant to sludging under oxidizing conditions of use. Still another object is the provision of a method of lubrication making use of such oils, containing the novel corrosion inhibiting ingredients herein disclosed.

This invention is based upon the discovery that oils of the classes above described, viz., moderately refined lubricant and insulating oils, solvent refined lubricant and insulating oils of high viscosity index, and highly refined lubricant and insulating oils may be stabilized against the deteriorating effects of oxidation and the formation thereby of corrosive agencies in the oil by the addition to the oil of a small amount of the oilsoluble, substantially water-insoluble reaction product produced by reacting an alkali salt of an alkyl or aralkyl xanthic acid with beta, beta dichlorethylether, which products are herein described as dixanthyl ethyl ethers.

Dixanthyl ethyl ethers may be prepared by the reaction of alkali xanthates with beta, beta dichlorethyl ether. Alkali xanthates or thiocarbonates are readily prepared by reacting an alcohol with carbon disulphide in the presence of an alkali such as potassium hydroxide. The reaction involved is of the type ROH+CS2+KOH ROSCSK+H2O where K may be potassium or sodium and where R is an alkyl, aralkyl, or other substituted alkyl radical. Many of these alkali xanthates are known and described in the literature. Examples of alkali xanthates useful for the purposes of this invention are the alkali salts of ethyl xanthate, isoamyl xanthate, isopropyl xanthate and benzyl xanthate. In general, the xanthic acid salts of any of the alkyl, aralkyl, or simply substituted alkyl radicals will be found useful, as for example, sodium n-butyl xanthate, potassium phenyl ethyl xanthate, potassium methyl ices Recreate RGUi/l Z2527. tomi osmoilt.

xanthate, potassium oleyl xanthate, potassium n-amyl xanthate, and sodium n-propyl xanthate.

We have found that alkali xanthates of the above group may be reacted with beta, beta dichlorethylether to form high boiling oils which are oil-miscible and substantially insoluble in water, and which possess the property of conferring upon petroleum fractions with which they are mixed an improved ability to resist the deteriorating effects of oxidation.

As an example of the preparation of one of these novel inhibitor ingredients, the preparation of diethyl xanthyl ethyl ether will be described. First, potassium ethyl xanthate was prepared in accordance with the reaction previously discussed. Then 32 parts of this potassium ethyl xanthate was dissolved in 320. parts (by weight) of ethyl alcohol. Then 14.3 parts of beta, beta dichlorethyl was added at room temperature (about 209-25 C.) and the mixture refluxed for 5 hours, at approximately 78 C. The mixture was allowed to stand overnight to settle the precipitate of potassium chloride, which was then removed by filtration. The filtrate was distilled for the removal of alcohol, after which the distillation residue was then up in benzol and washed with water to insure complete removal of any potassium chloride or of any remaining unreacted potassium ethyl xanthate. The benzol layer was then heated to 120 C. under 2.5 mm. pressure to remove benzol and unreacted beta, beta dichlorethylether. The product soobtained was a yellow oil, miscible in petroleum fractions and substantially insoluble in water.

The proportions of ingredients used were in the ratio of 2 mols of the alkali xanthate for 1 moi of beta, beta dichlorethylether. Sufficient ethyl alcohol was used to completely dissolve the alkali xanthate and to give a reaction mixture of suitable fluidity. Other solvents which might well be used are methylalcohol, propyl alcohol, or any solvent which is a mutual solvent forthe reacting compounds, and which does not itself react with the reagents.

It will be apparent to those skilled in the art that the reaction product resulting from interaction of an alkali xanthate and beta, beta dichlorethylether is probably a dialkyl xanthyl ethyl ether, formed according to the following reaction, in the case of an ethyl xanthate:

ClCzH4 CzHtOSCSCzHi As an example of the stabilizing or oxidation inhibiting effect of these novel ingredients when added to solvent fifined-motor oils of high viscosity index, the following test results are given:

A section of a bearing containing a cadmiumsilver alloy surface and weighing about 6.0 grams was put in 30 grams of a commercial automobile oil. The oil was heated to 175C. for 22 hours while a stream of air was bubbled against the surface of the bearing. The loss in weight of the bearing during this treatment measures the amount of corrosion that has taken place. The following results were obtained with the motor oil when tested alone and with the addition of various dixanthyl ethyl ethers. In each case a sample of the oil containing a stabilizer was run at the same time as a sample of the straight oil, each sample .containing a section cut from the same bearing.- The loss in weight of the bearing in the stabilized oil divided by the loss in weight of the bearing in the unstabilized oil gives the \UH Ufifi MU Milli UMUM relative corrosiveness of the former under these From the above it will be noted that small amounts of these novel stabilizer compounds are highly effective. In the above tests, the motor oil used was a solvent refined motor oil of high viscosity index, having the following characteristics:

S. A. E .20 Saybolt Visc 56" at 210 F. Flash point 425 F. VI 117 As an example of the stabilizing or oxidation inhibiting effect of these novel ingredients when added to highly refined oils, the-following test results are noted.

An oil that has been highly refined as by treatment with large amounts of sulphuric acid, or by other means such as solvent refining, has a tendency to oxidize readily, especially at elevated temperatures, and forms acidic oxidation products; greatly reduces the usefulness of an oil for electrical insulating purposes, as in transformers and cables, and for lubrication as in turbines. An oil of this type, with a specific gravity of .87, a Lovibond color of less than 0.1 and a Saybolt universal viscosity of 69 seconds at 100 F., was tested for stability by heating 150 grams to 120 The formation of these acidic products- C. and bubbling oxygen gas through it for hours. The amount of acidic oxidation products thus formed in the oil was found by titrating with caustic alkali and the results were recorded in terms of neutralization number (milligrams of KOH required to neutralize the acids formed in 1' gram of oil). The following results were thus obtained for this oil alone and for the same oil The proportion of these novel stabilizing compounds used in oil to accomplish the purposes of this invention will range from 0.01% to 1.0%, although it will be found preferable to use lower percentages within this range. In most casesa suitable degree of stabilization may be had with a concentration of 0.1% of the ingredient.

The novel stabilizing compounds herein disclosed are described as oil-miscible, which term is used in the sense that they are sufficiently soluble in oil to accomplish the purposes of this invention. They are likewise described as substantially water-insoluble, meaning that they are at least sufllciently water-insoluble to prevent their removal from an admixture with oil by contact with water such as might occur during storage, and/or handling, and/or use.

It will be understood that the exemplary preparation of one of the novel stabilizing compounds of this invention discussed herein is given only by way of example and is not in any way intended as a limitation. It is our invention to claim broadly all of the novelty inherent in this invention, subject only to those limitations expressed in the following claims.

We claim:

1. A refined petroleum oil of high boiling point, stabilized against the deterioration efiects of oxidation by the addition thereto of a small amount suificient to substantially inhibit oxidation of a compound of the general formula no s s can 0 R0 s c s CZHi where R is a radical selected from the group consisting of alkyl and aralkyl radicals.

2. A refined petroleum oil of high boiling point, stabilized against the deteriorating efiects of oxidation by the addition thereto of a small amount sufiicient to substantially inhibit oxidation of a dixanthyl ethyl ether.

3. A refined petroleum oil of high boiling point stabilized against the deteriorating effects of oxidation by the addition thereto of a small amount sufiicient to substantially inhibit oxidation of a dixanthyl ethyl ether, the xanthyl radicals of which are derived from radicals selected from the group consisting of methyl, ethyl, propyl, butyl, amyl, hexyl, isopropyl, isobutyl, isoamyl, lauryl, oleyl, stearyl, benzyl, and phenyl ethyl radicals.

4. A motor oil, stable against the formation of sludge and corrosive products therein by oxidation reactions under normal conditions of use, comprising a major proportion of a motor oil not so stable, and in admixture therewith a small amount, suflicient to substantially inhibit oxidation, of a dixanthyl ethyl ether, the xanthyl radicals of which are derived from radicals selected from the group consisting of methyl, ethyl, propyl, butyl, amyl, hexyl, isopropyl, isobutyl, isoamyl,

lauryl, oleyl, stearyl, benzyl, and phenyl ethyl radicals.

5. A motor oil of viscosity index greater than 75, stable against the formation therein by oxidation during use of materials corrosive to bearing metals selected from the group consisting of alloys of cadmium-silver, copper-lead, copperleadtin, cadmium-nickel, cadmium-zinc, cadmiumzinc hardened with lead, cadmium-zinc hardened with antimony and lead babbitts, comprising a major proportion of a petroleum lubricant of VI greater than '75 which is not so stable, and in admixture therewith a small amount, sufiicient to substantially inhibit such corrosion of a dixanthyl ethyl ether, the xanthyl radicals of which are derived from radicals selected from the group consisting of methyl; ethyl, propyl, butyl, amyl, hexyl,

isopropyl, isobutyl, isoamyl, lauryl, oleyl, stearyl,

benzyl, and phenyl ethyl radicals.

6. A highly refined petroleum oil of high boiling-point stable against the deteriorating efiects of oxidation tending to decrease the lubricating and dielectric qualities thereof, comprising a major proportion of a petroleum oil which is not so stable, and in admixture therewith a small amount, sufiicient to substantially inhibit oxidation, of a dixanthyl ethyl ether, the xanthyl radicals of which are derived from radicals selected from the group consisting of methyl, ethyl, pro pyl, butyl, amyl, hexyl, isopropyl, isobutyl, isoamyl, lauryl, oleyl, stearyl, benzyl, and phenyl ethyl radicals.

7. An improved mineral oil composition stabi lized against the deteriorating effects of oxida tion comprising a mineral oil fraction having in admixture therewith from about 9 to about 4% of a dixanthyl ethyl ether.

8. An improved mineral oil composition stabilized against the deteriorating effects of oxidation comprising a mineral oil fraction having in admixture therewith from about 1 6% to about of a dixanthyl ethyl ether selected from the group consisting of diethyl xanthyl ethyl ether, di-isopropyl xanthyl ethyl ether, and dibenzyl xanthyl ethyl ether.

ROBERT C. MORAN. EVEREI'I W. FULLER. 

